1366 - Incorrect integer value: '' for column 'customer_id' at row 1

insert into whos_online (customer_id, full_name, session_id, ip_address, time_entry, time_last_click, last_page_url) values ('', 'Guest', '14mc9cpsmeu77924asqp2cf1n0', '216.73.216.137', '1780008708', '1780008708', '/index.php?XTCsid=38f09672db884903e3803adf9d076819&language=en')

[XT SQL Error]